Witch is the best example of commensalism

I think it's number B.

The barnacles and whales one.

Commensalism is a type of symbiotic relationship between two organisms in which one benefits without affecting the other one is any way.

Examples of Commensalism for a Better Understanding of the Concept:

Cattle Egrets and Livestock.

Orchids Growing on Branches of Trees.

Remora Fish and Sharks.

Pseudoscorpions and Beetles.

Monarch Butterfly and Milkweed.

Birds Following Army Ants.

Burdock Seeds on the Fur of Passing Animals.

Barnacles and Whales.